Method and apparatus for starting a steam power plant



Jan. 5, 1965 o. CAPITAINE 3,163,991

METHOD AND APPARATUS FOR STARTING A STEAM POWER PLANT Filed Jan. 25,1963 By I f 4f Arron/rs United States Patent 3,163,991 METHOD ANDAPPARATUS FOR STARTING A STEAM POWER PLANT Detlev Capitaine, Kronshagen,near Kiel, Germany,

assignor to Sulzer Frres, S.A., Winterthur, Switzerland, a corporationof Switzerland Filed Jan. 23, 1963, Ser. No. 253,392 Claims priority,application Germany, Jan. 30, 1962, M 51,616 6 Claims. (Cl. 60-107) Thepresent invention relates to a method and means for starting a steampower plant, more particularly to a steam power plant including a forcedflow steam generator whose feedwater is preheated by steam from a sourceother than said steam generator, during the initial starting period ofthe plant.

When starting a steam power plant including a steam turbine it isdesired to operate the turbine a soon as possible after starting thesteam generator and it may be of advantage to start the turbine withsteam of a much lower pressure than the normal operating pressure. Inorder to reduce the time between starting the steam generator andstarting the turbine it is conventional to supply steam from a sourceother than the steam generator to a feedwater reservoir for preheatingthe feedwater for the steam generator before starting the steamgenerator and during the initial starting period thereof. This causes arise of the pressure in the feedwater reservoir.

Due to expansion of the heated water in the tubular heating surfaces ofthe steam generator a mixture of steam and water is formed therein andit has been proposed to conduct the operating medium, before its flowthrough the final heating sections, through a separator for separatingthe steam from the water. The flow rate of operating medium through thesteam generator before and immediately after starting heating of thesteam generator may be considerably greater than the flow rate of thelive steam required at that time.

The steam separated in the separator is conducted through the finalsections of the heating surfaces of the "ice forced flow steamgenerator, before and during the initial starting period of the steamgenera-tor, is conducted in a feedwater heater in heat exchange relationto the feedwater flowing from a turbine condenser to a feedwaterreservoir and from the latter into the steam generator. Aftertransferring most of its heat content to the feedwater the water isconducted to the condenser. In this way very little heat is Wasted bytransfer to the condenser coolant.

When, after the initial starting period, the pressure in the waterseparator is higher than that in the feedwater reservoir the waterseparated in the separator may be conducted directly into the feedwaterreservoir and no water is passed through the feedwater heater into thecondenser.

In plants wherein feedwater heaters are provided for heating feedwaterby means of steam tapped from the turbine during normal operation of theplant one of these feedwater heaters may be used for heating thefeedwater by means of hot water separated from the operating mediumflowing through the steam generator during starting of the plant and noadditional feedwater heater need be provided for carrying out the methodaccording to the invention.

In a preferred arrangement of the plant according to the invention thewater separator is connected to: the outlet of one of a plurality oftubular heating sections arranged in the steam generator in seriesrelation with respect to the flow of the operating medium through thesteam generator. The steam space of the separator is connected to theinlet of the subsequent heating section for delivering steam thereintofor further heating the steam. The outlet of the section wherefromoperating medium is conducted into the separator and the inlet for thesubsequent heating section whereinto the separated steam is conductedare interconnected by a valved conduit steam generator and the steamleaving the steam generator is used for heating the pipe leading to theturbine and for heating the turbine. Since the pressure in the separatoris lower than in the feedwater reservoir, the water separated in theseparator cannot be discharged into the reservoir and it has beenproposed to pump this water into the reservoir or into the feed pipebetween the reservoir and the steam generator. This requires at leastone pump in addition to the condensate pump and to the feed pump.

' It is also known to return the water separated in the separatordirectly or through a pressure-reducing device into the turbinecondenser. This involves loss of heat from the water to the condensercoolant.

It is an object of the invention to provide a method of and means foroperating a steam power plant having a forced flow steam generator and aturbine receiving steam therefrom whereby the time needed for warming upand starting the plant is shortened and heat which is wasted byconventional plants during these operations, is saved.

An object of the invention is to provide a method and means which affordrecovery of the heat contained in the water separated from the operatingmedium circulating through a forced flow steam generator during thestarting period. The method and means according to the invention avoidthe shortcomings of conventional systems and avoid the provision ofadditional pumps which increase first cost and operating expenses.

According to the invention hot water separated in a separator from theoperating medium flowing through a affording by-passing a controlledamount of operating medium around the separator. This avoids provisionof a separator which is so large as to pass all operating medium duringfull load operation at a reasonable pressure drop in the separator and awater separator can be provided which is just large enough to cope withthe requirements of the star-ting operation of the plant. During normaloperation only a portion or no operating medium may be passed throughthe separator and a portion or all of the operating medium is bypassedaround the separator.

The novel features which are considered characteristic of the inventionare set forth with particularity in the appended claims. The inventionitself, however, and additional objects and advantages thereof will bestbe understood from the following description of an embodiment thereofwhen read in connection with the accompanying drawing, the one figure ofwhich is a diagrammatic illustration of a plant according to theinvention.

Referring more particularly to the drawing, numeral 1 designates a steamgenerator having tubular heating surfaces including an economizer 2, andevaporator 3, a preliminary superheater 4, and a final superheatercomprising two sections 5 and 6; no heating means for the steamgenerator are shown. The sections 2, 3, 4, 5 and 6 are arranged inseries relation with respect to the flow A pipe 9 the pipes 9 and 11.The final superheater section 6 is connected to a high pressure turbine14 by means of a pipe 13. The operating medium expanded in the turbine14 flows through a pipe 15 to the reheater 7 and therefrom through apipe 16 to a low pressure turbine 17. After expansion of the operatingmedium in the low pressure turbine 17 the operating medium is conductedthrough a pipe 18 into a condenser 19. The condensate is pumped by apump 20 through a conduit 21 wherein low pressure preheaters 22 and 23are arranged in series relation, to a feedwater reservoir 24.

When starting the steam generator from. cold, foreign steam of apressure of about to atmospheres is supplied into the feedwaterreservoir 24 through a conduit 25. Feedwater is pumped from thereservoir 24 by means of a feed pump 26a through a conduit 26 whereinhigh pressure preheaters 27 and 28 are interposed, and through afeedwater control valve 32 into the economizer 2.

At this time, the operating medium passing through the sections 2, 3 and4 of the tubular heating system of the steamgenerator is a mixture ofsteam and water. The water is separated from the steam in the separator10 and the steam is conducted through the pipe 11 into the superheatersection 5. The water separated in the separator 10 is conducted througha valved pipe 29 into a heat exchanger 3% which is interposed in thepipe 21 between the low pressure heat exchanger 23 and the feedwaterreservoir 24. After transferring heat to the feedwater flowing'throughthe heat exchanger 3% the Water from the separator It is conductedthrough a pipe 31 into the condenser 19.

The feedwater heater 3% need not be an additional feedwater heater, butmay be one of the conventional feed- Water heaters which are heated bysteam tapped from the turbine 17.

A valved pipe 33 interconnects the separator 10 and the feedwaterreservoir 24 for conducting the water from the separator directly intothe reservoir 24 when, after the initial starting period, the pressurein the separator is higher than in the reservoir.

If desired, the pipe 31 may terminate in an auxiliary condenser, notshown.

I claim:

1. A method of starting a steam power piant including a forced flowsteam genera-tor and a turbine receiving steam therefrom, comprising, incombination:

heating the feedwater of said steam generator by means of steam from asource other than said steam generator,

conducting the heated feedwa-ter as operating medium through the steamgenerator,

separating water from operating medium flowing through and beforeleaving the steam generator, conducting steam remaining after separationof the Water through a portion of the steam generator, and conductingseperated Water in heat exhange relation with the feedwater before thefeedwater is heated by steam from a source other than the steamgenerator.

2. A method of starting a steam power plant including a forced flowsteam generator and a turbine receiving steam therefrom, comprising, incombination:

heating the feedwater of said steam genera-tor by steam from a sourceother thansaid steam generator, conducting the heated feedwater asoperating medium through the steam generator, conducting a portion ofthe operating medium flowing through the steam generator through aseparator and separating water from the operating medium,

conducting steam remainingafter separation of the water through aportion of said steam generator, and

conducting separated water in heat exchange relation with the feedwaterbefore the feedwater is heated by steam from a source other than thesteam generator.

3. A method of starting a steam power plant including a forced flowsteam generator, a steam turbine receiving steam from said steamgenerator, and a condenser receiv exhaust steam. from said turbine,comprising, in combination:

heating the feedwater of said steam generator by means of steam from asource other than said steam generator,

conducting the heated feedwater as operating medium through the steamgenerator,

separating water from operating medium flowing through and beforeleaving the steam generator, conducting steam remaining after separationof the water through a portion of the steam generator, conductingseparated water in indirect heat exchange relation wtih the feedwaterbefore the feedwater is heated by steam from a source other than thesteam generator, and conducting water which has been conducted in heatexchange relation with the feedwater into said condenser.

4. In a steam power plant having a forced flow steam generator, a steamturbine receiving steam from said generator, and a condenser receivingexhaust steam from said turbine, the combination of:

feedwater conduit means connecting said condenser to said steamgenerator for supplying feedwater to the latter,

a feedwater reservoir interposed in said feedwater conduit means,

a feedwater heater interposed in said feedwater conduit means upstreamof said reservoir,

steam supply means connected to said reservoir for supplying heatingsteam thereto from a source other than said steam generator, for heatingthe feedwater in said reservoir during starting of the plant,

said steam generator including a heating tube system for conductingoperating medium therethrough and heating the operating medium therein,and

a water separator interposed in said tube system for separating waterfrom the operating medium and returning the remaining steam to said tubesystem for further heating the steam,

said Water separator being connected to said feedwate-r heater forsupplying water separated in said separator as a heating agent to saidfeedwater heater for heating the feedwater therein.

5. In a steam power plant as defined in claim 4 and wherein said heatingtube system includes a plurality of heating sections arranged in seriesrelation with respect to the flow of the operating medium therethrough,said separator being connected to the outlet of one said sections forreceiving operating medium therefrom and to the inlet of the subsequentsection for delivering steam therein-to, a valved conduitinterconnecting said sections to: which said separator is connected anday-passing said separator for passing a controlled portion of operatingmedium around said separator.

6. In a steam power plant as defined in claim 4 a valved conduitconnected to said separator and to said reservoir for conducting waterseparated in said separator into said reservoir.

References Cited by the Examiner UNITED STATES PATENTS 2,989,038 6/61Schwarz 122406 3,008,295 11/61 Profos 60-107 X 3,016,712 1/62 Taylor60-107 X JULIUS E. WEST, Primary Examiner.

ROBERT R. BUNEVICH, Examiner.

1. A METHOD OF STARTING A STEAM POWER PLANT INCLUDING A FORCED FLOW STEAM GENERATOR AND A TURBINE RECEIVING STEAM THEREFROM, COMPRISING, IN COMBINATION: HEATING THE FEEDWATER OF SAID STEAM GENERATOR BY MEANS OF STEAM FROM A SOURCE OTHER THAN SAID STEAM GENERATOR, CONDUCTING THE HEATED FEEDWATER AS OPERATING MEDIUM THROUGH THE STEAM GENERATOR, SEPARATING WATER FROM OPERATING MEDIUM FLOWING THROUGH AND BEFORE LEAVING THE STEAM GENERATOR, CONDUCTING STEAM REMAINING AFTER SEPARATION OF THE WATER THROUGH A PORTION OF THE STEAM GENERATOR, AND CONDUCTING SEPARATED WATER IN HEAT EXCHANGE RELATION WITH THE FEEDWATER BEFORE THE FEEDWATER IS HEATED BY STEAM FROM A SOURCE OTHER THAN THE STEAM GENERATOR. 